Who else could upstage the Duchess of Cambridge other than a feline movie star? That’s exactly what happened when Kate attended the London premiere of A Street Cat Named Bob last night.

After arriving on the red carpet in a beautiful white dress by Self-Portrait—featuring a full-length skirt split to the thigh and a crochet bodice—Kate was introduced to the eponymous Bob, an 11-year-old ginger cat.

Bob was dressed in a fetching scarf and lying on a red cushion (typical movie star) when he and the duchess were introduced, and allowed the royal to pet him briefly behind the ears.

But she was uncertain of how to judge Bob’s mood. “Is that purring or growling?” she asked his owner, James Bowen, who later described his pet as “a bit of the king in the house.”

A Street Cat Named Bob stars Luke Treadaway as James (and Bob as himself) and is based on James’ book about how a stray cat helped him overcome his heroin addiction.

Kate was in attendance at the premiere on behalf of Action on Addiction, a charity of which she is patron.

Of Bob (who he calls his “baby boy”) James said, “He showed me that everybody has a second chance in life if they want it.

“He made me see the need to get clean so that I could take care of him and in turn take care of myself.”

James took care of Bob when he was a stray cat recovering from an injury, and from then on Bob followed him everywhere—even onto the bus when James was heading into London city center to go busking.

“He came and asked me for help, and he needed me more than I needed to abuse my own body,” said James.

“He is what I wake up for now… He’s definitely given me the right direction to live my life.”